H&B told me 1095. The bits are laminated/forge welded so it looks to me it's a 1095 core between lower carbon sides. It's a full length/width piece too. I confirmed with by etching the top and bottom of my latest H&B - a custom Mammen style Viking Axe - with hot apple cider vinegar.
H&B's heat treat seems to be pretty good to me. When I got my newest one I took it down to my woodpile and beat the dickens out of it and threw it some. It's plenty sturdy and the edge retention is good.